Random homologous pairing and incomplete sister chromatid alignment are common in angiosperm interphase nuclei |
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Authors: | Veit Schubert Young-Min Kim Alexandre Berr Jörg Fuchs Armin Meister Sylvia Marschner Ingo Schubert |
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Institution: | (1) Leibniz Institute of Plant Genetics and Crop Plant Research (IPK), Corrensstrasse 3, 06466 Gatersleben, Germany;(2) Present address: Institute of Plant Molecular Biology (IBMP), 12, rue du Général Zimmer, 67084 Strasbourg, France |
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Abstract: | The chromosome arrangement in interphase nuclei is of growing interest, e.g., the spatial vicinity of homologous sequences
is decisive for efficient repair of DNA damage by homologous recombination, and close alignment of sister chromatids is considered
as a prerequisite for their bipolar orientation and subsequent segregation during nuclear division. To study the degree of
homologous pairing and of sister chromatid alignment in plants, we applied fluorescent in situ hybridisation with specific
bacterial artificial chromosome inserts to interphase nuclei. Previously we found in Arabidopsis thaliana and in A. lyrata positional homologous pairing at random, and, except for centromere regions, sister chromatids were frequently not aligned.
To test whether these features are typical for higher plants or depend on genome size, chromosome organisation and/or phylogenetic
affiliation, we investigated distinct individual loci in other species. The positional pairing of these loci was mainly random.
The highest frequency of sister alignment (in >93% of homologues) was found for centromeres, some rDNA and a few other high
copy loci. Apparently, somatic homologous pairing is not a typical feature of angiosperms, and sister chromatid aligment is
not obligatory along chromosome arms. Thus, the high frequency of chromatid exchanges at homologous positions after mutagen
treatment needs another explanation than regular somatic pairing of homologues (possibly an active search of damaged sites
for homology). For sister chromatid exchanges a continuous sister chromatid alignment is not required. For correct segregation,
permanent alignment of sister centromeres is sufficient. |
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Keywords: | Arabidopsis Brachycome Cohesion Secale Sister chromatid separation Zea |
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